The present invention is related to displaying a composite image using multiple projected images, and particularly to method and apparatus for projecting multiple images using a single light source.
Seamless integration of images from multiple projectors has many applications in the simulation, visualization and virtual reality (VR) fields. The images are typically generated by computers, specialty cameras, or specially prepared media (e.g., multi-channel image generators). Recently, use of such technology has become widespread in various industries and government applications including, without limitation, training and simulation, oil/gas, automotive, aerospace, education, as well as command and control.
Pre-formatted output of a multi-channel image generator is typically sent to several video projectors that are carefully arranged and aligned to a geometry that precisely matches the output format of the generators. In order for this arrayed display to create an image that appears perfectly contiguous, a number of factors should generally be managed:
1) The geometry and alignment of the projectors should typically be precisely matched with the output geometry of the multi-channel image generator;
2) The color balance of the multiple projectors should typically be precisely matched so that the images from these projectors have matching color balances; and
3) Adjacent images should typically be edge blended to generate a seamless projected composite image.
A method typically used to generate a seamless composite image from multiple projectors is to overlap a portion of the images and then using smoothing, correction or ramping factors on each side of the overlap, to blend the brightness of the overlapping images together so that they appear uniform. The correction or smoothing factors may also be used to boost minimum black levels of non-overlapped regions to match the minimum black level of the overlapped region without affecting rest of the signal levels in the non-overlapped regions.
Examples of making a seamless composite image from multiple projectors are described in U.S. Pat. No. 4,974,073 entitled xe2x80x9cSeamless Video Display,xe2x80x9d U.S. Pat. No. 5,136,390 entitled xe2x80x9cAdjustable Multiple Image Display Smoothing Method and Apparatus,xe2x80x9d U.S. Pat. No. 6,115,022 entitled xe2x80x9cMethod and Apparatus for Adjusting Multiple Projected Raster Images and U.S. patent application Ser. No. 09/876,513 entitled xe2x80x9cMethod and Apparatus for Seamless Integration of Multiple Video Projectorsxe2x80x9d filed Jun. 6, 2001, the contents of all of which are incorporated by reference herein.
The projector technologies used for these arrayed or tiled displays have changed in the past few years from principally cathode ray tube (CRT) projectors to various formats of display engines that include Liquid Crystal Display (LCD), Image Light Amplification (ILAxe2x80x94Hughes/JVC), Digital Light Projection (DLPxe2x80x94Texas Instruments) L-Cos (Liquid Crystal on Silicon) and others, which may be referred to as digital projectors.
Digital projectors typically use some form of variable reflectivity or translucence to form images and project the images by applying a constant light source to the images having variable reflectivity or translucence. This is in contrast to CRT, which uses variable luminance of the cathode ray tube as opposed to variable reflectivity or translucence.
Maintaining all segments of a projected composite image to have the same precise color balance to create a contiguous arrayed display has been a challenge with CRT in that each red, blue and green phosphor tube typically should be carefully adjusted to behave the same on each projector. Additionally, with usage and component aging, the color balances often drift and change, thus requiring constant maintenance.
CRT projectors allow warping of images by changing the scanning path of the electron beam that is exciting the phosphors to glow. This allows adjustment of the display geometry to curves, off-axis presentation and fine tuning separate red, blue and green phosphor tubes to another, both for single full color images and for multiple images, which may include overlapping segments. However, since the CRT projectors are typically large and have three large heavy lenses for each of red, green and blue image channels, setting up and maintaining geometric alignment of multiple CRT projectors have been a daunting task. Therefore, an additional challenge with CRT arrays has been the setup and maintenance of geometric alignment of the images relative to one another.
Therefore, it is desirable to provide a digital projector that overcomes one or more challenges associated with color balancing and geometric alignment of CRT projectors, while allowing adjustment to match projection geometries.
In an embodiment according to the present invention, a projection system is provided. The projection system comprises an image source, a light source and a beam splitter. The image source is used for generating a plurality of images to be projected. The light source is used for providing light to be used for projecting the images. The beam splitter is used for splitting the light from the light source to apply a corresponding portion of the light to each of the images.
In another embodiment according to the present invention, a method of projecting a plurality of images is provided. The plurality of images and light for applying to the images are generated. The light is split into light portions, and the images are projected by applying the light portions to the images.